The invention generally relates to manually operated valves that heretofore have been used only on freight railcars equipped with conventional pneumatic brake control valves to vent air from the brake cylinders. More particularly, the invention pertains to a release valve apparatus designed for freight railcars equipped with electrically controlled pneumatic (ECP) brake control valves.
The following background information is provided to assist the reader to understand at least one of the many environments in which the invention could be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless expressly stated otherwise in this document.
A freight train typically includes one or more locomotives, a plurality of railcars and several trainlines. For a freight train headed by a locomotive equipped with an ECP brake control system, the trainlines include both pneumatic and electrical lines some of which run from the lead locomotive to the last railcar in the train. A pneumatic trainline known as the brake pipe is one such trainline. It extends the length of the freight train, as does a two-wire electrical trainline known as the ECP trainline. Each locomotive also features a multi-wire electrical trainline known as the multiple unit (MU) line cable. The MU line cable consists of 27 different electrical lines. As is well known in the railroad industry, the MU line cable contains 74V dc power and return lines on which battery power from the locomotive is supplied to the ECP brake equipment on each railcar and to various other power consuming devices on the train.
The brake pipe consists of a series of pipe lengths, with one pipe length secured to the underside of each railcar. As shown in FIG. 1, each pipe length has, at each of its ends, a flexible hose 1 with a coupler commonly referred to as a glad hand 2. As the locomotives and other rail vehicles are coupled in sequence to form the freight train, the brake pipe 3 is formed by connecting the glad hand 2 at the end of each pipe length to the glad hand 2 of another such pipe length on an adjacent vehicle. Similar to the brake pipe 3, the conduit in which the ECP trainline 4 is housed actually constitutes a series of individual conduits. One such conduit secured to the underside of each vehicle interconnects to another such conduit via a connector between each rail vehicle. Supplied from the 74V dc power line of the MU line cable in the locomotive, the ECP trainline 4 typically operates at a nominal 230V dc to power the ECP brake equipment on each railcar of the freight train.
The ECP brake control system in the locomotive includes a cab station unit and a master controller from which the brakes on the train are ultimately controlled. The cab station unit features one or two handle(s) and/or push buttons that the train operator uses to direct control of the brakes. One such handle, known as the automatic brake handle, can be moved to and between the following positions: release, minimum service, full service, suppression, continuous service, and emergency. Between the minimum and full service positions lies the service zone wherein each incremental movement of the handle toward the full service position causes an even stronger service application of the brakes. The force with which the brakes apply depends on how far towards the full service position the brake handle is moved.
Inputs from the handle(s) and/or push buttons are processed by the cab station unit and then passed to the master controller. Operating according to instructions contained within its programming code, and in response to the inputs from the handle(s) and other sources, the master controller formulates a brake command appropriate to current conditions and transmits it along the ECP trainline 4 to each railcar in the freight train. As specified by the American Association of Railroads (AAR), the brake commands and other ECP messages are transmitted from the locomotive using a powerline communications system such as the Echelon LonWorks System. Along the ECP trainline 4, the brake command(s) are then conveyed to the ECP brake equipment on each railcar via branch wiring 5. Similarly, in a manner known in the railroad industry, the brake pipe 3 connects to the ECP brake equipment on each railcar via a branch pipe 6.
The master controller can thus order, through the brake command, any action from a release of brakes to an emergency application of brakes or any degree of brake application in between those two extremes. The brake equipment may also be designed to provide graduated release of the brakes. The degree of brake application ordered by the master controller is typically conveyed in terms of a percentage of the pressure required for full service brake application. For example, zero percent (0%) is typically designated for a release of brakes, 15% for a minimum service brake application, 100% for a full service brake application and 120% for an emergency brake application.
The ECP brake equipment on each railcar typically includes an auxiliary reservoir 10, an emergency reservoir 20, one or more brake cylinders 30, a retainer valve 40, a car control unit (CCU) 50 and an ECP brake control valve, generally designated 60. The ECP brake control valve 60 includes a pneumatic portion 61 and an electropneumatic portion, generally denoted 63, typically mounted to opposite sides of a pipe bracket 62. The pneumatic portion may take the form of an emergency portion of a brake control valve such as an ABD, ABDX or ABDW type valve made by the Westinghouse Air Brake Technologies Corporation (WABTEC). The electropneumatic portion 63 is comprised of a manifold 100, several pressure transducers, and several solenoid-operated application and release valves. The transducers and solenoid valves are collectively designated by section 200. The manifold 100 defines several ports to which the transducers and solenoid valves connect. It also defines a number of internal passages, which communicate with passages internal to the pipe bracket 62.
Each port of the pipe bracket 62 connects to one of the interconnecting pipes on the railcar such as those leading to the brake pipe 3, the retainer valve 40, the auxiliary reservoir 10, the emergency reservoir 20 and the brake cylinder 30. It is through the internal passages of the pipe bracket 62 that the various portions of the brake equipment communicate fluidly with the pneumatic piping on the railcar. Used to monitor the pressures in the brake pipe 3, the two reservoirs 10 and 20 and the brake cylinder 30, the pressure transducers convey electrical signals indicative of those pressures to the CCU 50.
Each CCU 50 includes a transceiver and a microprocessor. Controlled by the microprocessor, the transceiver is connected via the branch wiring 5 to the ECP trainline 4 from which it receives the brake commands issued by the master controller. The transceiver converts the electrical brake commands into a form usable by the microprocessor. Operating according to its programming code and to the dictates of the brake commands and other electrical signals it has received, the microprocessor controls the application and release valves in a manner well known in the brake control art. It is through the solenoid valves that air can be maintained within, exhausted from, or directed from either or both of the reservoirs to the brake cylinder(s) 30.
By moving the automatic brake handle into service zone, for example, the train operator in the locomotive will cause the ECP brake control system to issue a service brake command along the ECP trainline 4. In response to the service brake command, the microprocessor on each railcar will then energize the application valve(s) for the appropriate time. This enables the appropriate amount of air to flow from the auxiliary reservoir 10 and/or the emergency reservoir 20 via the pipe bracket 62 and the manifold 100 through the application valve(s) ultimately to the brake cylinder 30. Similarly, in response to the brake handle having been moved into the release position, the ECP brake control system will issue a release brake command along the ECP trainline 4. In response to this command, each microprocessor will then energize the release valve(s) on its railcar. Air from the brake cylinder 30 will then flow via the pipe bracket 62 and the manifold 100 through the release valve(s) to atmosphere, thus depressurizing the brake cylinder 30 and releasing the brakes on the railcar.
In addition, as a safety measure, emergency brake commands are conveyed to the railcars not only electrically along the ECP trainline 4 but also pneumatically along the brake pipe 3. By moving the handle into the emergency position, the train operator in the locomotive causes the pressure in the brake pipe 3 to drop at an emergency rate. This drop in pressure eventually propagates along the brake pipe 3 to each railcar in the train. Should the CCU 50 and/or the electropneumatic portion 63 lose power or otherwise fail, the emergency portion 61 of brake control valve 60 will still respond pneumatically to the telltale reduction in pressure that occurs in the brake pipe 3 during an emergency. The emergency portion 61 is designed to respond to the emergency pressure drop by supplying pressurized air from both reservoirs 10 and 20 to the brake cylinder 30, and thereby cause an emergency application of the brakes. Absent a command to apply the brakes and under conditions known in the brake control art, the ECP brake equipment through its pneumatic valves 7 and 8 (as shown in FIG. 2) charges the two reservoirs 10 and 20 with pressurized air obtained from the brake pipe 3.
However pressurized, the brake cylinder 30 converts the pressurized air that it receive to mechanical force. This mechanical force is transmitted by mechanical linkage to the brake shoes. Forced against the wheels and/or disc brakes, the brake shoes are used to slow or stop the rotation of the wheels. The magnitude of the braking force applied to the wheels is directly proportional to the pressure built up in the brake cylinder(s) 30.
Before the advent of ECP brake control systems, freight trains were equipped with only conventional pneumatic or electropneumatic brake control systems. ECP brake control systems were initially employed only as an overlay for or an adjunct of the conventional brake control systems. Unlike an ECP brake control system, a conventional control system uses the brake pipe to convey pneumatically from the locomotive to every railcar in the train all brake commands, not just the emergency commands.
In addition to the cab station unit, a conventional brake control system includes a brake control computer (BCC) and a pneumatic operating unit (POU). The BCC responds to the signals output by the cab station unit, i.e., by the handle(s) and/or push buttons. Based on these and other signals and on the software that dictates its operation, the BCC controls the operation of various pneumatically and electropneumatically operated devices that comprise the POU. Comprised mainly of pneumatic logic circuitry and solenoid operated valves, these devices are commonly referred to as operating portions. It is through these operating portions that the BCC actually controls the pressure in the brake pipe (and in various other pneumatic trainlines and reservoirs).
The railcars on such conventionally equipped trains each have ABD, ABDX, ABDW or similar type conventional brake control valves (CBCV). This type of brake control valve has an emergency portion, like the one discussed above, along with a service portion, both mounted to a pipe bracket. Through the ports and internal passages of the pipe bracket, the service and emergency portions of the CBCV communicate fluidly with the pneumatic piping on the railcar, i.e., to the interconnecting pipes leading to the brake pipe, the brake cylinder and the two reservoirs.
The operator in the locomotive of such a conventionally equipped train also controls the brakes through the automatic brake handle. In a conventional system, however, the operator, by moving the handle, controls the pressure level in the brake pipe and thereby directs whether, and to what extent, the brakes will apply. By changing its pressure level, the brake pipe is used to pneumatically convey release, service and emergency brake commands to the CBCV on every railcar. In response to a release brake command (i.e., when brake pipe pressure is restored to its normal operating pressure), the service portion of the CBCV not only charges the two reservoirs with the pressurized air it receives from the brake pipe but also vents the brake cylinder to atmosphere thereby causing the brakes on the railcar to release. In response to a service brake command (i.e., when brake pipe pressure is reduced at a service rate), the service portion supplies air from only the auxiliary reservoir to the brake cylinder to apply the brakes. How much the brake pipe pressure is reduced, and thus the magnitude of the service brake application, depends on how far the automatic brake handle is moved towards the full service position. In response to an emergency brake command (i.e., when the brake pipe is vented to atmosphere at an emergency rate), the service and emergency portions of the CBCV supply air from both reservoirs to the brake cylinder to apply the brakes more quickly and forcefully.
Under the control of a conventional brake control system, the brake pipe (or, more accurately, the pressure level contained within it) determines whether a CBCV will charge its two reservoirs or deliver pressurized air previously stored in one or both of its reservoirs to the brake cylinder. In an ECP brake control system, by contrast, the ECP trainline 4 is the conduit through which the brake equipment on each railcar is controlled.
One major difference between ECP and conventional brake control systems is that only brake control valves designed for the latter have been equipped with a manually operated valve known as a release valve portion. Bolted to the service portion of a conventional brake control valve (CBCV), the release valve portion has typically provided three levels of operation from which a railroad worker can choose. Specifically, it offers a choice between exhausting only the brake cylinder, exhausting the auxiliary reservoir and the brake cylinder, or exhausting both reservoirs and the brake cylinder. An example of such a release valve portion is shown and described in Publication 5062-19 published by WABTEC and incorporated herein by reference.
Such a release valve portion contains certain internal passages, and typically houses a handle valve assembly and a spool valve assembly. The passages are designed to interconnect the various parts and chambers of the handle and spool valve assemblies with specific passages internal to the service portion of the CBCV. By moving the handle of the handle valve assembly, a railroad worker can manually affect the internal operation of the valve assemblies, and in turn control whether and which of the known passages in the service portion will be operatively linked with the passages in the release valve portion.
On ABD, ABDX and ABDW type brake control valves, for example, the extent to which the handle is moved determines the operation of the release valve portion. A temporary pull on the handle compels the release valve portion to rapidly exhaust the brake cylinder to atmosphere through the spool valve assembly, while retaining the air stored in the auxiliary and emergency reservoirs. The brake cylinder will generally stay locked in the release position by the spool valve assembly until the control pressure, provide by the brake pipe, rises to a set level. A sustained partial movement of the handle not only allows the brake cylinder to vent as noted above but also permits the auxiliary reservoir to vent via the handle valve assembly. Moving the handle to its fullest extent likewise compels the release valve portion to vent the brake cylinder, but also permits both reservoirs to vent via the handle valve assembly.
The advent of electronics compelled the development of ECP technology. The performance of ECP technology has enabled the service and emergency braking functions on freight trains to be carried out much faster than was possible with conventional pneumatic technology. This increase in speed is because the brake commands are conveyed to the railcars electrically on the ECP trainline 4 rather than pneumatically via the brake pipe 3. Although it may use the same emergency portion as a conventional brake control valve, the ECP brake control valve has obviated the need for the service portion, which has been succeeded by the electropneumatic portion 63 described above. Operating in conjunction with the CCU 50, the electropneumatic portion 63 is what enables the ECP brake control valve to speedily initiate service and emergency braking on today""s modern freight trains.
One shortcoming in the ECP brake control valve, however, is that it lacks a manually operable release valve. This is largely due to the loss of the brake pipe as a carrier of control pressure (service brake commands) and to the configuration of the manifold 100, which has networks of internal passages substantially different from those found in the service portions of conventional brake control valves. Due to the lack of such release valves on railcars equipped with ECP brake equipment, railroad workers are currently unable to easily vent the brake cylinders, either alone or in combination with one or both of the reservoirs.
It is, therefore, an objective of the invention to provide a manually operable release valve apparatus for an ECP brake control valve.
Another objective is to provide a release valve apparatus designed to operate through the internal passages of a manifold of an electropneumatic portion of an ECP brake control valve.
A further objective is to provide a release valve apparatus for an ECP brake control valve that can be used not only to manually release the pressure from a brake cylinder after a brake application but also to lock the brake cylinder in a release state until the release valve apparatus is automatically reset.
Still another objective is to provide a release valve apparatus that can be used to exhaust not only the brake cylinder but also the auxiliary reservoir and/or the emergency reservoir.
In addition to the objectives and advantages listed above, various other objectives and advantages of the invention will become more readily apparent to persons skilled in the relevant art from a reading of the detailed description section of this document. The other objectives and advantages will become particularly apparent when the detailed description is considered along with the accompanying claims and the attached drawings.
The foregoing objectives and advantages are attained by a release valve apparatus that permits the pressure within a brake cylinder of a railcar to be released manually. The railcar will typically have at least one reservoir and an electropneumatic valve used in controlling the pressure developed within the brake cylinder. In a basic embodiment, the release valve apparatus comprises a control valve assembly, a spool valve assembly and an enclosure. The enclosure defines a control valve housing and a spool valve housing in which the control and spool valve assemblies are housed, respectively. It also defines at least one supply channel, a brake cylinder passage, an exhaust passage, a brake control passage, a control chamber, a chamber passage and a release passage. The supply channel serves to connect the reservoir with the control valve housing. The brake cylinder passage serves to connect the brake cylinder with the spool valve housing. The exhaust passage communicates the spool valve housing to atmosphere, and the brake control passage serves to connect the electropneumatic valve with the spool valve housing. The control chamber communicates with one end of the spool valve housing, and the chamber passage further links the control chamber with the spool valve housing. The release passage interconnects the control and spool valve housings. The spool valve assembly includes a spool member and a reset spring. The position of the spool member in the spool valve housing dictates whether and which of the passages communicate. Biased by the reset spring to a deactivated position, the spool member therein permits the brake control and the brake cylinder passages to communicate through the spool valve housing. This allows the pressure in the brake cylinder to be controlled via the brake control passage. In the deactivated position, the spool member also connects the chamber and release passages thereby permitting only the control valve assembly to control pressure in the control chamber. The spool member responds to the build up of pressure in the control chamber by moving away from the deactivated position. The spool member first moves to switch the brake control passage from communication with the brake cylinder passage to communication with the chamber passage. By connecting the brake control and chamber passages, the spool member enables pressure to be built in the control chamber via both the brake control and release passages. The continuing pressure buildup in the control chamber then moves the spool member to the released position. When so forced to the released position, the spool member cuts off communication between the release and chamber passages. This causes the pressure in the control chamber to be controlled only through the brake control passage. In the released position, the spool member also links the brake cylinder and exhaust passages, causing the brake cylinder to vent to atmosphere. The spool member remains locked in the released position until the pressure in the control chamber is vented via the brake control passage. The venting of the control chamber then enables the reset spring to reset the spool member to the deactivated position. The control valve assembly has a release lever, a lifter assembly and a lifter spring. The lifter spring biases the lifter assembly into a closed position wherein the supply channel is cut-off from the release passage. When operated, the release lever forces the lifter assembly into an open position wherein the supply channel communicates with the control valve housing. This allows air from the reservoir to flow to the spool valve housing through the release passage. It also allows the air from the reservoir to flow past the control valve assembly to atmosphere. The release valve apparatus can thus be used not only to manually release the pressure in the brake cylinder after a brake application but also to lock the brake cylinder in a release state until pressure in the control chamber is vented via the brake control passage.
In accordance with an aspect of the invention, a plurality of annular flanges is formed around the spool member. Between each of the annular flanges lies an annular passageway. The annular passageways of the spool member enable the passages of the enclosure to communicate according to the position that the spool member occupies in the spool valve housing. Each annular flange defines an annular groove in which an o-ring is secured to resist leaking between adjacent annular passageways.
In accordance with another aspect of the invention, the lifter assembly includes an auxiliary check valve, an emergency check valve, a lifter member, a first plunger and a second plunger. This lifter assembly is designed to work with a railcar on which at least two reservoirs are disposed. The at least one supply channel will then comprise first and second channels. The first channel connects the auxiliary reservoir with the control valve housing, and the second channel connects the emergency reservoir with the control valve housing. More specifically, the auxiliary check valve is disposed in the first channel between the auxiliary reservoir and the release passage. The emergency check valve lies in the second channel between the emergency reservoir and the release passage. The lifter member is biased by the lifter spring against the release lever to the closed position. The first plunger lies between the auxiliary check valve and the lifter member, and the second plunger lies between the emergency check valve and the lifter member. According to this aspect, the operation of the release lever forces the lifter member against at least one of the plungers to open at least one of the check valves. This allows air from at least one of the reservoirs to flow through the control valve housing and the release passage to the spool valve housing. It also allows the air to flow past the lifter member and release lever to atmosphere, thereby permitting the auxiliary and/or emergency reservoir(s) to vent to atmosphere.
In accordance with yet another aspect of the invention, the release lever includes a base portion and a rod portion. The base portion lies in contact with the lifter member inside the enclosure, with the rod portion extending away from the enclosure. The lifter member has a diameter slightly less than that of the control valve housing providing a clearance therebetween. The base portion defines a vent duct therethrough. By operating the rod portion to hold open the check valves, air from one or both reservoirs is allowed to flow via the clearance and past the base portion of the release lever to atmosphere.